1. Field of the Invention
This invention relates generally to liquid container systems, and more particularly to systems and methods for measuring a level of a liquid in a tank.
2. Description of Related Art
Motor vehicles with internal combustion engines typically run on a liquid fuel such as gasoline stored in a fuel tank. Such vehicles typically include a fuel level monitoring system for indicating an amount (i.e., level) of the liquid fuel in the fuel tank. Most fuel level monitoring systems include a sending unit mounted in the fuel tank and a moving coil meter viewable by an operator of the vehicle. The sending unit and the moving coil meter are electrically connected in series. The moving coil meter includes a moving coil that rotates about a central axis. A pointer connected to the moving coil indicates the level of the liquid fuel in the fuel tank. An electrical resistance of the sending unit is dependent upon the level of the liquid fuel in the fuel tank, and determines a magnitude of an electrical current flowing through the sending unit and the moving coil meter. When the level of the liquid fuel in the fuel tank changes, the moving coil rotates, and the connected pointer indicates the change in the level of the liquid fuel.
In many known fuel level monitoring systems (i.e., fuel gauge systems), particularly those used in motor vehicles manufactured in the United States, the electrical resistances of the sending units in the fuel tanks are a maximum when the tanks are full and a minimum when the tanks are empty. A problem arises in such systems in that the maximum resistances of the sending units typically vary considerably. In order to ensure that fuel gauges read full at all possible maximum resistances of the sending units, the systems are typically configured such that the fuel gauges read full at fuel levels that are often substantially below full. As a result, as a level of fuel in a fuel tank begins to drop, a typical fuel gauge continues to read full, then drops relatively quickly from full to empty. This non-linear behavior of fuel gauges causes them to be highly inaccurate.
In order to give a motor vehicle operator as much time as possible to select a refueling facility, it would be beneficial to have a more accurate fuel gauge system.